Steinway Musical Instruments announced on Monday that it had agreed to be acquired by the private equity firm Kohlberg & Company in a deal worth roughly $438 million.

The offer of $35 a share represents a 33 percent premium over Steinway’s average closing price in the 90 trading days that ended June 28. Compared with the average closing price during the 52 weeks that ended June 28, the offer represents a premium of 45 percent, the company said.

.........................In buying Steinway, the firm plans to “accelerate its global expansion, while ensuring the artisanal manufacturing processes that make the company’s products unique are preserved, celebrated and treasured,” Christopher W. Anderson, a Kohlberg & Company partner, said in a statement.